It is known in the art to form flutes at a low helix angle (i.e. high lead) or a high helix angle (i.e. low lead). A “low helix” (or low helical flute) is a flute that helically “winds” around a cylinder at an angle of no more than 45 degrees. A “super” slow-helical flute would be a flute that winds around a cylinder at an angle of at no more than 15 degrees. A “high helix” (or high helical flute) is a flute that helically winds around a cylinder at an angle of greater than 45 degrees, while a “super” high-helical flute winds around a cylinder at an angle of at least 65 degrees. Low helix angle flutes are typically employed for rough cutting while high helix angle flutes are employed for finish cutting.
Straight flute or slow helix spiral flute is widely used in shallow blind hole tapping. They have better mechanical strength than high helix spiral flute and can usually generate tightly-curled chips. However, they cannot be applied to deep hole tapping due to its limited chip lifting force. A high helix flute (or low lead) is required for chip evacuation, but are often subject to bird nesting or chip wrap.
Approximately 60% of all tapping is in blind hole applications and most these holes are tapped with spiral flute taps. Long chipping materials require a fast spiral flute helix angle (>30°) which is also subject to bird nesting or chip wrap. This is one of the most challenging problem in the tapping world. None of the tap existing on the market today truly solves this problem.
The present invention has been developed in view of the foregoing.